ALT Top graph: changes in acanthodian mean skeletal completeness through time: all data plotted (at bottom, in black); without isolated fin spine data in solid purple line; wihtout isolated scale taxa in dark pink dashed line; without isolated scale or fin spine taxa in yellow dashed line at the top. Time scale runs from upper Ordovician (Katian) on the left to the lower Triassic (Olenekian) on the right. Bottom plot: violin plots showing the distribution of skeletal completeness between different acanothodian subgroups, with Acanthodiformes on the left being the most complete, and Tchunacanthida on the far right being least complete.